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Meandering Rivers

River meanders are one of the most ubiquitous patterns in fluvial morphology. For many years the beauty and applicative importance of these nearly regular loops in river planimetry have attracted the interest of several researchers in fluid mechanics and morphodynamics, geomorphology, river engineering, riparian ecology, and petroleum engineering. From a physical point of view, meandering rivers form a dynamical system far from equilibrium, which, in its continuous evolution, exhibits some kind of statistical stationarity. The river evolution is driven by fluid dynamic and morphodynamic processes, which cause lateral bank erosion and the continuous migration of meanders, as well as by sporadic cutoffs that prevent self-intersections of the river and produce sudden reductions in river length and sinuosity (see Figure 1). These internal dynamics are usually forced by external deterministic or stochastic factors, with different temporal and spatial scales, due to hydrological and riparian processes as well as to pedological, geological, and anthropic constraints. Our interest is in the mathematical modeling of the fluid dynamic and morphodynamic processes that are responsible for the short-term and long-term evolution of rivers.

Dynamic and geometric role of cutoff.The dynamics of a meandering planimetry is characterized by (i) a continuous elongation, (ii) a downstream (sometimes upstream) migration of the bends, and (iii) the occurrence of cutoff events, which even though sporadic, are recognized to induce important geomorphic changes. In the past, the study of the cutoff event have been carried out following the descriptive or the numerical approach. Empirical laws relating the hydraulics to geomorphological parameters were obtained, and several important aspects emerged, such as the attainment of a statistical steady state governed by typical temporal and spatial scales.